\[\begin{array}{l}
b,B = (x + 1)({x^7} - {x^6} + {x^5} - {x^4} + {x^3} - {x^2} + x - 1)\\
= {x^8} - {x^7} + {x^6} - {x^5} + {x^4} - {x^3} + {x^2} - x + {x^7} - {x^6} + {x^5} - {x^4} + {x^3} - {x^2} + x - 1\\
= {x^8} - 1\\
Voi:x = 2\\
= > B = {2^8} - 1 = 256 - 1 = 255\\
c,C = (x + 1)({x^6} - {x^5} + {x^4} - {x^3} + {x^2} - x + 1)\\
= {x^7} - {x^6} + {x^5} - {x^4} + {x^3} - {x^2} + x + {x^6} - {x^5} + {x^4} - {x^3} + {x^2} - x + 1\\
= {x^7} + 1\\
Voi:x = 2\\
= > C = {2^7} + 1 = 128 + 1 = 129\\
d,D = 2x(10{x^2} - 5x - 2) - 5x(4{x^2} - 2x - 1)\\
= 20{x^3} - 10{x^2} - 4x - 20{x^3} + 10{x^2} + 5x\\
= x\\
Voi:x = - 5\\
= > D = - 5\\
Bai5:\\
a,A = ({x^3} - {x^2}y + x{y^2} - {y^3})(x + y)\\
= [{x^2}(x - y) + {y^2}(x - y)](x + y)\\
= (x - y)({x^2} + {y^2})(x + y)\\
= ({x^2} - {y^2})({x^2} + {y^2})\\
= {x^4} - {y^4}\\
Voi:x = 2,y = - 1/2\\
= > A = {2^4} - {(\frac{{ - 1}}{2})^4}\\
= 16 - \frac{1}{{16}}\\
= \frac{{255}}{{16}}\\
b,B = (a - b)({a^4} + {a^3}b + {a^2}{b^2} + a{b^3} + {b^4})\\
= {a^5} + {a^4}b + {a^3}{b^2} + {a^2}{b^3} + a{b^4} - {a^4}b - {a^3}{b^2} - {a^2}{b^3} - a{b^4} - {b^5}\\
= {a^5} - {b^5}\\
Voi:a = 3,b = - 2\\
= > B = {3^5} - {( - 2)^5}\\
= 243 - ( - 32)\\
= 275\\
c,C = ({x^2} - 2xy + 2{y^2})({x^2} + {y^2}) + 2{x^3}y - 3{x^2}{y^2} + 2x{y^3}\\
= {x^4} + {x^2}{y^2} - 2{x^3}y - 2x{y^3} + 2{x^2}{y^2} + 2{y^4} + 2{x^3}y - 3{x^2}{y^2} + 2x{y^3}\\
= {x^4} + 2{y^4}\\
Voi:x = - 1/2;y = - 1/2\\
= > C = {(\frac{{ - 1}}{2})^4} + 2.{(\frac{{ - 1}}{2})^4}\\
= \frac{1}{{16}} + 2.\frac{1}{{16}}\\
= \frac{3}{{16}}
\end{array}\]